KR20020078137A - method for manufacturing ceramic materials with a sound absorption by using a foaming agent - Google Patents

Abstract

PURPOSE: Provided is a manufacturing method of ceramic sound absorbing materials with continuous porosity by adding a large quantity of foam to clay paste. Also, the sound absorbing materials with exhaust gas purification are manufactured by coating sound absorbing materials with TiO2 powder. CONSTITUTION: The manufacturing method of ceramic sound absorbing materials is as follows: mixing clay paste with solidifying materials such as gypsum, cement, bentonite and limestone; adding a large quantity of foam to be total porosity of 30-90%; drying at 70deg.C for 12hrs and cooling; sintering at 1200deg.C; coating sintered sound absorbing materials with TiO2(anatase) by fixing TiO2 powder, photocatalyst, drying at 110deg.C and thermal treating under 650deg.C. The resultant ceramic sound absorbing materials have the effects of sound absorbance, and exhaust gas purification due to the adsorption of SOx and NOx.

Description

Method for manufacturing ceramic materials with a sound absorption by using a foaming agent}

The present invention relates to a sound absorbing material that absorbs noise generated by roads, railroads, factories, etc., and its manufacture is performed by forming a continuous void by using cohesive force of bubbles in clay paste, and condensing before bubbles are bubbled, and then firing through a drying process. To make it. Furthermore, by fixing the fine titanium dioxide (TiO ₂ ) powder, developed as a photocatalyst raw material, on the surface as a heat-treatment on the sound absorbing material manufactured, it absorbs SO _X and NO _X in automobile exhaust gas, thereby absorbing noise and purifying automobile exhaust gas. It is to provide a body sound absorbing material.

Sound-absorbing materials used for sound-absorbing walls are divided into (1) types of glass wool, rock wool and organic fibers, (2) porous concrete, and (3) types of lightweight foam concrete. can do.

(1) Glass fiber, rock wool, and organic fiber have the advantage of being economical and sound-absorbing, but they do not have their own shape-holding power and are harmful to human body and are restricted in use.

(2) A representative example of lightweight foamed concrete is ALC (Autoclaved Lightweight Concrete). ALC is composed of lime, siliceous raw material, blowing agent and admixture as the main raw materials. It is prepared by mixing slurry with water to make slurry and curing in a high temperature and high pressure autoclave to form structurally stable calcium silicate hydrate crystal. ALC has excellent disadvantages of insulation and sound insulation because of the formation of independent voids in concrete, but relatively low sound absorption.

To solve this problem, a large amount of foaming agent is added to the cement paste filed by the present applicant to form a continuous void, and there is a "method of manufacturing a sound absorbing material having continuous void" (application number 10-2000-0017343), but the compressive strength by mixing a large amount of foam It has a disadvantage in that the wind safety is low because it is small to 13 ~ 34kgf / ㎠.

(3) Porous concrete is usually made by crushing cement paste on crushed stone and artificial and natural light aggregates. Recently, its application to sound absorbing materials and plant plants has been studied. However, when applied as a sound-absorbing substitute material, the porosity is about 5-30%, so the sound absorption rate is small and the sound absorption rate of the mid-low bass region is very low due to the particle size of the aggregate compared to the fibrous material.

In addition, the sound absorbing material absorbing the exhaust gas is (1) used as a fine aggregate of porous concrete using artificial zeolite known to absorb NO _x , and (2) by applying titanium dioxide, a photocatalyst, to the sound absorbing material. The research is largely classified as a purifying research.

(1) When granulated artificial zeolite is used as aggregate of porous concrete, the internal surface area is increased, and the surface area is rich in irregularities, which can be used as sound-absorbing concrete, as well as concrete that absorbs particularly harmful NO _x from exhaust gases from automobiles. It is also suggested that it can be used. However, artificial zeolites have a disadvantage in that the removal rate of NO ₂ , which accounts for 3-4% of nitrogen oxides, is high at 70-85%, while the adsorption removal rate of NO, which occupies 95%, is low, at 7-10%.

(2) a photocatalyst (Photocatalyst) air purification technology by may be applied to a concrete product which construction or the like of nitrogen oxide (NO _x) is a high road year contamination concentration by removing oxidation contaminants of the photocatalytic surface with ultraviolet light have. However, high heat treatment around 600 ° C. for coating titanium dioxide, a photocatalyst, on concrete lowers the durability of concrete having a heat resistance temperature around 500 ° C.

Accordingly, the present invention is to develop a sound absorbing material for purifying exhaust gas by coating titanium dioxide on a ceramic material which has no problem during high temperature coating of photocatalyst.

An object of the present invention is to produce a continuous air-absorbing material having a high sound absorption rate and high strength as a rigid sound absorbing material. Furthermore, by fixing the fine titanium dioxide (TiO ₂ ) powder developed as a photocatalyst raw material on the surface by heat-treatment in the manufactured sound absorbing material, it absorbs SO _X and NO _X in automobile exhaust gas, thereby absorbing noise and purifying automobile exhaust gas. Its purpose is to provide a method for producing a body-shaped sound absorbing material.

1 is a sound absorption rate according to the specimen thickness change

Sound absorbing material manufacturing method of the present invention for achieving the above object,

Mixing the coagulant in the clay paste to coagulate the clay mixture before air bubbles added to the clay paste are deflected;

Mixing the foaming agent bubbled into the mixture so that the total porosity is 30 to 90% to form continuous voids in the clay paste;

The technical gist of the present invention relates to a method for producing a sound absorbing material having a continuous void comprising a firing step of drying and ceramicizing the mixture.

In addition, after the titanium dioxide (Tio ₂ ) powder is applied to the manufactured sound absorbing material, an exhaust gas purification function by a photocatalyst may be added.

Hereinafter, the present invention will be described in detail.

The present invention finds a phenomenon in which bubbles are continuously connected due to their cohesive force, a technique for forming bubbles in the clay paste by continuous cohesion, and a technique for condensing bubbles in the clay paste before they are bubbled. It was successful in deriving it.

The process of forming a continuous bubble in the clay paste is subjected to the [1] mixing step, [2] aggregation step, [3] coagulation step, [4] drying step and firing step, and [5] titanium dioxide treatment step.

[1] mixing stages

After mixing the coagulant in the clay paste and adding a large amount of bubbles generated by using the bubble generator to the clay paste, the mixing order of the clay paste, the coagulant and the bubbles may be changed or mixed at the same time. In this experiment, the surface tension was lowered by increasing the dilution ratio of the foaming agent to stabilize the foam.

[2] flocculation stages

Bubbles exist as independent spheres, and there is a cohesion force to adhere to each other. The bubbles mixed with the clay paste by the cohesion force push the surrounding clay paste and show the phenomenon that the bubbles and the bubbles come into contact with each other. Thus, in the present invention, the continuous voids are formed by pushing the clay paste surrounding the bubbles by the cohesive force that a myriad of large and small independent bubbles try to stick to each other and contact each other. Bubble cohesion is affected by the fluidity and viscosity of the clay paste. When the amount of clay paste is large, independent voids are formed, and when the amount of bubbles is large, continuous voids are formed. Therefore, it is preferable to mix the addition amount of foaming agent so that the total porosity which can form a continuous space | gap becomes 30 to 90%.

[3] condensation

The clay paste pushed out by the cohesive force of the bubbles starts to dry, and a specimen having continuous pores is formed inside the specimen. The continuous pores of the specimens form the continuous pores where the agglomerated parts of the bubbles, that is, the clay pastes are not buried, and the bubbles are in contact with each other.

Therefore, it is important to allow the bubbles to form continuously, which is possible only if the bubbles remain in the clay in their shape until the clay is dry and retains its shape. However, the bubbles in the clay mixture are expanded or contracted by factors such as drying of the mixture, temperature difference of outside air, drying and shaking of the air, and the clay mixture becomes a vesicle before the clay mixture is dried to maintain its shape. Bubble phenomena in the clay mixture cause about 48 hours after casting the specimen, causing settling. To solve this, it is necessary to dry the clay paste as soon as possible before the air bubbles are deflected. However, the clay paste mixed with bubbles is difficult to rapidly dry, and since the bubbles are parceled out during drying, condensation works such as gypsum, cement, bentonite, limestone, etc. It is necessary.

[4] drying and firing steps

After the condensation is finished, the temperature rise rate is 5 ° C / hour for 12 hours at the highest temperature of 70 ° C, and the temperature of the drying furnace is gradually lowered so that there is no significant difference with the temperature of the outside air. Dried over. As a firing method, it was raised to 100 ° C per hour and calcined around 1200 ° C.

[5] titanium dioxide treatment

In order to add the exhaust gas purification function to the sound absorbing material, titanium dioxide as a photocatalyst was fixed to the sound absorbing material. In the method of fixing the anatase type titanium dioxide to the sound absorbing plate, the titanium dioxide powder is dispersed in a liquid such as water or alcohol, adhered to the material surface, dried at 110 ° C., and then fixed to the material surface by heat treatment. In this case, the higher the heat treatment temperature, the more strongly it can be fixed to the surface and the acid resistance is improved, but when the temperature is higher than 650 ℃, the photocatalytic function is greatly reduced. This is because the crystal form of titanium dioxide changes from the anatas type to the rutile type when the temperature rises, the crystal grows significantly, the surface activity decreases, and the photocatalytic function decreases.

Therefore, the heat treatment temperature is considered to be less than 650 ℃.

The sound absorbing material of the present invention can adjust the porosity to 30 to 90%, and is light in weight, excellent in heat insulation and soundproofing, and non-flammable.

Hereinafter, the present invention will be described in detail through examples.

(Example)

The mixing ratio of clay and water is 70%, and the coagulant is replaced with 20% and 30% of the weight of clay and gypsum to prepare a clay paste, and then a foaming agent solution having a dilution ratio of 10%, which is a high alcoholic ester compound After the bubble was generated using the bubble generator, bubbles were mixed by 3 to 9% of the clay and gypsum weight to prepare a bubble slurry. After condensing it into a dry container for 72 hours in a predetermined container, the heating rate is 5 ° C per hour in the drying furnace, and it is continued for 12 hours at the highest temperature of 70 ° C. After drying through the cooling process using an electric furnace was raised to 100 ℃ per hour and fired around 1200 ℃.

The mixing ratio of gypsum 30% is shown in Table 1 below.

Disclosure Name (%) Unit clay amount (kg / m ³ ) Water-clay ratio (%) Gypsum replacement amount (clay + gypsum) ×% Foaming agent addition amount (clay + gypsum) X% Gypsum 30%-bubble 7% 1000 70 30 7

Table 2 shows the physical properties of the specimens prepared by adding bubbles having a dilution ratio of 10% to 3, 5, 7, 9% of the weight of clay and gypsum for the specimens of Table 1.

Bubble addition amount ((clay + gypsum) *%) Continuous Porosity (%) Major Porosity (%) importance Permeability coefficient (cm / sec) 3 8 31 0.99 0 5 15 50 0.79 0.001 7 34 60 0.54 0.006 9 41 64 0.41 0.013

Table 2 shows the tendency that the continuous porosity and the total porosity inside the specimen increase as the amount of bubble addition increases. In 3% of bubble addition, the continuous porosity was 8% and the total porosity was 31%, and in 9%, the continuous porosity was 41% and the porosity was 64%. Can be.

The sound absorption rate of the ceramic sound absorbing material manufactured when using gypsum as a foaming agent and a coagulant with 30% clay and plaster weight is shown in [Fig. 1]. This figure shows that the sound absorption is increased in the bass region as the thickness increases. have.

Table 3 shows the sound absorption and average sound absorption rates of specimens using 20% and 30% of gypsum as the coagulant weight.

As shown in Table 3, the average sound absorption of the ceramic sound absorbing material produced by the present invention is represented by 57% at 3 cm, 65% at 5 cm, and 7 cm at 72 cm, indicating good sound absorption performance.

In addition, after applying titanium dioxide to the ceramic sound-absorbing material having a diameter of 10 cm, No gas removal rate and No ₂ generation rate measured by chemiluminescence by oxidizing No gas with a photocatalyst are shown in Table 4.

This table shows 70% removal rate and 10% NO ₂ generation rate, which is about 10 times higher than that of zeolite having 7 ~ 10% NO removal rate when NO gas is introduced at 2ℓ / min. Purifying action is shown. In addition, this ceramic sound absorbing material does not change the NO removal rate and NO ₂ generation rate even after cleaning the surface with washing water, suggesting that it can be used repeatedly.

As mentioned above, the present invention

(1) It is possible to manufacture a rigid sound absorbing material having continuous voids without sedimentation of the clay and air bubbles.

(2) The manufactured sound absorbing material satisfies 70% of the average sound absorption rate notice of the Ministry of Environment,

(3) Titanium dioxide can be applied to the sound absorbing material to purify automobile exhaust gas.

(4) The compressive strength of the sound absorbing material is 45 to 65 kgf / cm 2, which is a sound absorbing material with excellent strength.

Claims (3)

Mixing the coagulant in the clay paste to coagulate the clay mixture before air bubbles added to the clay paste are deflected; Mixing the foaming agent bubbled into the mixture so that the total porosity is 30 to 90% to form continuous voids in the clay paste; Drying and firing the mixture; Method for producing a ceramic sound absorbing material having a continuous void comprising The method for producing a sound absorbing material according to claim 1, wherein the substitution rate of gypsum, cement, bentonite, and limestone as a coagulant has a range of 70% or less based on the weight of the clay and the coagulant. The method of manufacturing a sound absorbing material according to claim 1, wherein after applying titanium dioxide, a coating treatment is performed at a temperature of 650 ° C. or less to purify exhaust gas.